. >> i knew jack kennedy. jack kennedy was a friend of mine. senator, you're no jack kennedy. >> reporter: memorable moments. but hardly game-changers. while presidential debates can affect the outcome of an election, vice presidential debates, like this week's upcoming match-up between vice president joe biden and his gop challenger, paul ryan, are a different animal. >> you need to see that each candidate has hit the standard of readiness. that they will be ready to step into the oval office and take the reins of the presidency. beyond that, in terms of the actual debate itself, unless there is a star killing or catching moment, it rarely changes the course of the debate. >> reporter: democratic strategist, donna brazil, says, the first rule here, do no harm. >> try not breaking new ground. this is not an audition of 2016. this is about 2012. >> i don't like a damn thing about him. no. >> reporter: biden, who participated in more than 20 debates and forums in the 2008 campaign, says the contests are never easy. >> what i've been doing mostly